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January 25, 2020 compiler error when trying to get random key from AA | ||||
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I have this code: import std.random; import std.stdio; void main() { auto aa = ["one": 1, "two": 2, "three": 3]; writeln(aa); auto rnd = rndGen; auto word = aa.byKey.choice(rnd); writeln(word); } And in the D playground it gives this error: onlineapp.d(8): Error: template std.random.choice cannot deduce function from argument types !()(Result, MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)), candidates are: /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599): choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng) with Range = Result, RandomGen = MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u) must satisfy the following constraint: isRandomAccessRange!Range /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609): choice(Range)(auto ref Range range) I am treating aa as a set and want to pick a random word from it. What am I doing wrong? I'm sorry I can't give a link to this code in the D playground but the URL in the web browser is just https://run.dlang.io/ and when I click Shorten to get a URL nothing seems to happen (using Firefox on Linux). |
January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to mark | On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote:
> I have this code:
>
> import std.random;
> import std.stdio;
> void main()
> {
> auto aa = ["one": 1, "two": 2, "three": 3];
> writeln(aa);
> auto rnd = rndGen;
> auto word = aa.byKey.choice(rnd);
> writeln(word);
> }
>
> And in the D playground it gives this error:
>
> onlineapp.d(8): Error: template std.random.choice cannot deduce function from argument types !()(Result, MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)), candidates are:
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599):
> choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng)
> with Range = Result,
> RandomGen = MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)
> must satisfy the following constraint:
> isRandomAccessRange!Range
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609):
> choice(Range)(auto ref Range range)
>
> I am treating aa as a set and want to pick a random word from it.
> What am I doing wrong?
>
> I'm sorry I can't give a link to this code in the D playground but the URL in the web browser is just https://run.dlang.io/ and when I click Shorten to get a URL nothing seems to happen (using Firefox on Linux).
rndGen is a range.
Use `auto word = aa.byKey.choice(rnd.front())` as index instead.
Then `rndGen.popFront()` to advance.
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January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to Basile B. | On Saturday, 25 January 2020 at 08:59:23 UTC, Basile B. wrote: > On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote: >> I have this code: >> >> import std.random; >> import std.stdio; >> void main() >> { >> auto aa = ["one": 1, "two": 2, "three": 3]; >> writeln(aa); >> auto rnd = rndGen; >> auto word = aa.byKey.choice(rnd); >> writeln(word); >> } >> >> And in the D playground it gives this error: [snip] >> I am treating aa as a set and want to pick a random word from it. >> What am I doing wrong? >> >> I'm sorry I can't give a link to this code in the D playground but the URL in the web browser is just https://run.dlang.io/ and when I click Shorten to get a URL nothing seems to happen (using Firefox on Linux). > > rndGen is a range. > > Use `auto word = aa.byKey.choice(rnd.front())` as index instead. > Then `rndGen.popFront()` to advance. I tried that. It doesn't solve the problem but does reduce the size of the error output to: onlineapp.d(9): Error: template std.random.choice cannot deduce function from argument types !()(Result, uint), candidates are: /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599): choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng) /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609): choice(Range)(auto ref Range range) |
January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to Basile B. | On Saturday, 25 January 2020 at 08:59:23 UTC, Basile B. wrote:
> On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote:
>> [...]
>
> rndGen is a range.
>
> Use `auto word = aa.byKey.choice(rnd.front())` as index instead.
> Then `rndGen.popFront()` to advance.
no sorry, I didn't read and thought you need the index of rndGen.
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January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to mark | On Saturday, 25 January 2020 at 09:06:53 UTC, mark wrote:
> On Saturday, 25 January 2020 at 08:59:23 UTC, Basile B. wrote:
>> On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote:
>>> [...]
> [snip]
>>> [...]
>>
>> rndGen is a range.
>>
>> Use `auto word = aa.byKey.choice(rnd.front())` as index instead.
>> Then `rndGen.popFront()` to advance.
>
> I tried that. It doesn't solve the problem but does reduce the size of the error output to:
>
> onlineapp.d(9): Error: template std.random.choice cannot deduce function from argument types !()(Result, uint), candidates are:
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599):
> choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng)
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609):
> choice(Range)(auto ref Range range)
yeah indeed. sorry, I didn't read and thought you needed the index of rndGen, e.g index % upperBound.
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January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to mark | On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote:
> I have this code:
>
> import std.random;
> import std.stdio;
> void main()
> {
> auto aa = ["one": 1, "two": 2, "three": 3];
> writeln(aa);
> auto rnd = rndGen;
> auto word = aa.byKey.choice(rnd);
> writeln(word);
> }
>
> And in the D playground it gives this error:
>
> onlineapp.d(8): Error: template std.random.choice cannot deduce function from argument types !()(Result, MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)), candidates are:
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599):
> choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng)
> with Range = Result,
> RandomGen = MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)
> must satisfy the following constraint:
> isRandomAccessRange!Range
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609):
> choice(Range)(auto ref Range range)
>
> I am treating aa as a set and want to pick a random word from it.
> What am I doing wrong?
>
> I'm sorry I can't give a link to this code in the D playground but the URL in the web browser is just https://run.dlang.io/ and when I click Shorten to get a URL nothing seems to happen (using Firefox on Linux).
So the problem is that byKey is not a ref parameter, so you can use array on it:
---
import std.random;
import std.stdio;
import std.array;
void main()
{
auto aa = ["one": 1, "two": 2, "three": 3];
writeln(aa);
Random rnd;
auto word = choice(aa.byKey.array, rnd);
writeln(word);
}
---
sorry for the previous noise.
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January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to mark | On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote:
> I have this code:
>
> import std.random;
> import std.stdio;
> void main()
> {
> auto aa = ["one": 1, "two": 2, "three": 3];
> writeln(aa);
> auto rnd = rndGen;
> auto word = aa.byKey.choice(rnd);
> writeln(word);
> }
>
> And in the D playground it gives this error:
>
> onlineapp.d(8): Error: template std.random.choice cannot deduce function from argument types !()(Result, MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)), candidates are:
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599):
> choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng)
> with Range = Result,
> RandomGen = MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)
> must satisfy the following constraint:
> isRandomAccessRange!Range
> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609):
> choice(Range)(auto ref Range range)
>
> I am treating aa as a set and want to pick a random word from it.
> What am I doing wrong?
>
> I'm sorry I can't give a link to this code in the D playground but the URL in the web browser is just https://run.dlang.io/ and when I click Shorten to get a URL nothing seems to happen (using Firefox on Linux).
So the problem is that byKey is not a ref parameter, so you can use array on it:
---
import std.random;
import std.stdio;
import std.array;
void main()
{
auto aa = ["one": 1, "two": 2, "three": 3];
writeln(aa);
Random rnd;
auto word = choice(aa.byKey.array, rnd);
writeln(word);
}
---
sorry for the previous noise.
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January 25, 2020 Re: compiler error when trying to get random key from AA | ||||
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Posted in reply to Basile B. | On Saturday, 25 January 2020 at 09:18:01 UTC, Basile B. wrote:
> On Saturday, 25 January 2020 at 08:35:18 UTC, mark wrote:
>> I have this code:
>>
>> import std.random;
>> import std.stdio;
>> void main()
>> {
>> auto aa = ["one": 1, "two": 2, "three": 3];
>> writeln(aa);
>> auto rnd = rndGen;
>> auto word = aa.byKey.choice(rnd);
>> writeln(word);
>> }
>>
>> And in the D playground it gives this error:
>>
>> onlineapp.d(8): Error: template std.random.choice cannot deduce function from argument types !()(Result, MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)), candidates are:
>> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2599):
>> choice(Range, RandomGen = Random)(auto ref Range range, ref RandomGen urng)
>> with Range = Result,
>> RandomGen = MersenneTwisterEngine!(uint, 32LU, 624LU, 397LU, 31LU, 2567483615u, 11LU, 4294967295u, 7LU, 2636928640u, 15LU, 4022730752u, 18LU, 1812433253u)
>> must satisfy the following constraint:
>> isRandomAccessRange!Range
>> /dlang/dmd/linux/bin64/../../src/phobos/std/random.d(2609):
>> choice(Range)(auto ref Range range)
>>
>> I am treating aa as a set and want to pick a random word from it.
>> What am I doing wrong?
>>
>> I'm sorry I can't give a link to this code in the D playground but the URL in the web browser is just https://run.dlang.io/ and when I click Shorten to get a URL nothing seems to happen (using Firefox on Linux).
>
> So the problem is that byKey is not a ref parameter, so you can use array on it:
Well the explanation for your error is rather that byKey did not verify isRandomAccesRange, i.e indexable by an index so .array on it solve this.
pfff finally ...
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